EDIT: I misunderstood what the user I was replying to said. His numbers are for EXACTLY zero, one, and two copies and my numbers are for AT LEAST 1-5 copies. Different things. Both our numbers are in agreement. Sorry Nilsoncsj!!!

I am sorry, it has been a LONG time since I took statistics but are you sure about that math? I been doing it in a spreadsheet and I get some different numbers.

For the probability of k successes the formula is:

P(n,k)=Overall chance

n=number of rolls

k=number of successes

p=probability

Now for an at least one success you take the chance of zero successes and subtract that number from one. So,

X=1-P(n,k)

For 50 rolls and a chance of 1.5% for a solo rate up SR the probability of zero successes is

P(50,0)={50!/[(50-0)! x 0!]} x 0.015^0 x (1-0.015)^(50-0)=0.4697%

X=1-0.4697=0.5303

or 53.03% of getting at least one SR.

Which is different from your value of 46.97%

Now, if I am remembering it correctly for at least two successes you would add the chance of zero successes to the odds of only one success and subtract that from one.

Odds of ONLY one success:

P(50,1)={50!/[(50-1)! x 1!]} x 0.015^1 x (1-0.015)^(50-1)=50 x 0.015 x .4768=.3576

Odds of at least 2 successes:

X=1-(0.4697+.3576)=.1727 or 17.27%

Putting this all in a spreadsheet I get the following for a solo rate up SR:

What I get for an SSR: